The present invention relates to a color still image sensing apparatus and method using a solid-state image sensing device.
Conventionally, the following color image sensing apparatus systems using solid-state image sensing devices such as a CCD (Charge Coupled Device), and the like are available.
(1) Three-plate Type Color Camera
Incident light is separated into three primary colors with an optical system (prism), and the separated three components of colors are respectively received with three solid-state image sensing devices. With the three-plate type color camera, since the three color components can be extracted at the same time, and an independent processing system is used for each color component, ideal image sensing characteristics can be obtained.
However, with this type of color camera, three solid-state image sensing devices are required, the color-separation optical system is complex, and the three solid-state image sensing devices require high attachment precision, resulting in an expensive system.
(2) Single-plate Type Color Camera
In a camera of this type, color filters are attached to the individual pixels (photoelectric conversion elements) of a solid-state image sensing device to obtain color information from a single solid-state image sensing device. The color filters normally used have a mosaic or stripe pattern in which primary colors or complementary colors are arranged in correspondence with the individual pixels. In this single-plate type color camera, no special color-separation optical system is required unlike in the three-plate type, and only one solid-state image sensing device is required, resulting in an inexpensive system.
However, since information extracted from one pixel pertains to a single color, and insufficient color information is compensated for using information of the neighboring pixels, such compensation may cause production of false colors (moire) or a low resolution.
(3) Color Filter Switching Single-plate Type Color Camera
In this camera, a single solid-state image sensing device is used, and color filters inserted in the optical path from the object to the solid-state image sensing device are switched in turn in synchronism with the charge transfer timings of the solid-state image sensing device, thereby extracting color information. A color still image is obtained by accumulating and synthesizing the extracted color information. In this case, a technique of improving the resolution by a pixel shift method is available (Japanese Patent Laid-Open No. 6-181546).
In this color filter switching type, image quality as high as that of the three-plate type can be obtained by a single plate. However, since relatively large color filters are, for example, rotated to sequentially convert the colors of light entering the solid-state image sensing device, image sensing input requires a long time, and the apparatus becomes bulky.